Latex particles obtained by emulsion polymerization can have a variety of applications, including for use as model colloids for calibration of instruments used to measure particle size, for immobilization of biomolecules (such as proteins or peptides) on the surface of the particles, for development of new types of immunoassays, and for film formation for ink-jet printing, painting, and coating applications. A commonly used method for connecting biological molecules, dye molecules, or the like, to the surface of latex particles is by physical or passive adsorption. However, resulting colloid systems tend to be less stable. Such instability can be avoided by covalently bonding biomolecules, dye molecules, or the like, to latex particulates of an emulsion. While functionalized latex particulates have applications in these and other fields, the ink-jet ink imaging application can be used to favorably illustrate unique advantages of the invention. Specifically, there has been great improvement in the area of water durability of ink-jet inks through incorporation of certain ink-jet compatible latex polymers. When printed as part of an ink-jet ink, a latex component of the ink can form a film on a media surface, entrapping and protecting the colorant within the hydrophobic print film.
This being the case, there is a continuing need to provide improved methods of preparing latex particulates having functional groups on the surface, which can in turn be used for chemical reaction with target molecules. One example of such a functional group is an amino group, which is quite reactive. To prepare amino-functionalized latex polymer particles, there have been several methods proposed. One method has been by copolymerization of methacrylates containing hydroxyl and carbonyl groups, which are chemically modified to have an amino group on the surface. Other methods have included post-polymerization of copolymers of styrene and chloromethyl styrene, the modification of carbonyl surface groups, or the nitration of polystyrene and reduction to amino groups. All of these methods can result in colloid systems that lack stability due to changes in the medium conditions, resulting in part from chemical reaction that occurs to provide the amino functional group.